List collections, size and count of documents on MongoDB

collection_size.py

from pymongo import MongoClient

MONGO_URI = ''
DATABASE_NAME = ''

client = MongoClient(MONGO_URI)
db = client[DATABASE_NAME]
collections = db.collection_names()

def readable_size(file_size):
    index_unit = 0
    units = ['byte', 'kB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];

    while (file_size > 1024):
        file_size = file_size / 1024;
        index_unit += 1

    return "{0:.2f} {unit}".format(round(file_size, 2), unit=units[index_unit])

stats = {}
for collection in collections:
    col_stats = db.command('collstats', collection)
    stats[collection] = {
        'count': col_stats['count'],
        'size': readable_size(col_stats['size'])
    }
    print collection + ' Collection size: {size} / Documets count: {count}'.format(
        size=stats[collection]['size'],
        count=stats[collection]['count'])